Audi A4 B7 2.0 TFSI engine oil leak
 

Hello,

I have recently bought an Audi A4 Convertible 2.0 TFSI (2006) with cylinder head damage.
I have put a second hand cylinder head on the engine, new camshaft timing chain and tensioner new camshaft seals, new camshaft adjuster cover gasket, new head gasket, cylinder head gasket cover, intake and exhaust gaskets.
I have also remove the oil pan to check the oil pump which was working fine and the con rod bearings which were good as well.
New sealant was applied to fit the oil pan back.

After I fitted everything back I put oil in the engine and I have observed an oil leak coming from the back of the engine.
I have assumed that the oil pan has not seal good with the block but after I have started the engine it doesn't look to come from there.
The oil leak is coming right above the oil pan between the block and the transmission.
when I checked with the oil pan out the flywheel was completely dry, so I assume that is not coming from rear main seal or from oil pan.

What else could it be?

I have made a few pictures after I applied some developer spray to indicate the leak.
Many thanks. https://cimg8.ibsrv.net/gimg/www.aud...ef0b8ba62e.jpg
https://cimg9.ibsrv.net/gimg/www.aud...8354e90f70.jpg
https://cimg0.ibsrv.net/gimg/www.aud...d5e266740a.jpg